A liquid crystal display panel, in which a pixel portion and a driver circuit are integrated over the same glass substrate utilizing a thin film transistor (hereinafter, also referred to as a “TFT”) using a crystalline semiconductor film having a thickness of several ten nanometers, is developed. Further, technique for manufacturing a CPU (Central Processing Unit) having a function as a center of a computer using high-performance polycrystalline silicon which is superior in a crystalline property, is reported (For example, refer to Non-Patent Document 1: Imaya, A., “CG Silicon technology and its application”, AM-LCD 2003 Digest, p. 1, 2003 and Non-Patent Document 2: Lee, B. Y., et al., “A CPU on a glass substrate using CG-Silicon TFTs”, ISSCC Digest, p. 164, 2003). According to such technical progress, feasibility of a system panel integrating a display function and a function of a computer realized by a CPU over a glass substrate has been increased.
A liquid crystal display panel is applied as a display means attached to various electronic devices and a study of using plastic or a plastic film as a substrate for a display substrate mainly used as a portable electronic device has been advanced. A plastic material has a feature capable of being thinned since the plastic material has low specific gravity, lightweight, and has high impact resistance compared with glass.
However, a plastic material is generally poor in heat resistance; therefore, a highest temperature of processing is required to be lowered and a high-quality crystalline semiconductor film has not been able to be formed even today. Hence, a system panel as described above had not been able to be realized.